Presser foot for shoe sewing machines



Oct. 24, 1950 v, PEDERSEN 2,527,196

PRESSER FOOT FOR SHOE SEWING MACHINES Filed Feb. 18, 1948 Patented Oct. 24, 1950 OFFICE PRESSER FOOT FOR SHOE SEWING MACHINES 1 Vilhelm Pedersen, Hong, Denmark Application February 18, 1948, Serial No. 9,274 In Denmark February 10, 1940 Section 1,- Public Law 690, August 8, 1946 Patent expires February 10, 1960 By the commonly known welt sewing-machines for footwear, sewing with an awl and needle, the sole is kept pressed together between asewing-table and a presser foot while the awl is pressed through the leather in the direction of the presser foot. The presser foot on these known machines is fastened on a rotatable arm actuated by a spring, this arm being provided with a fixed and a loose gear-segment (pawl-segments) with their centre in the point of rotation of the arm and co-acting with pawls controlled by a curve on the main shaft of the machine.

The pawls will partly lock the presser foot, and partly impart to the same an extra pressure for compression, as mentioned above, which is performed irrespective of the thickness of the material to be sewn.

This mechanical locking and unlocking of the presser foot has several. drawbacks. Firstly, an

accurate and complete locking in position can" not be accomplished with all-thicknesses of ,material, on account of the distance necessary between the teeth on the pawl-segment, and thereby the sewing will not be as uniform as desirable.

Nextly, the pawl will be rather quicklyworn,

wherefore it must be replaced by a new one and, finally, the manufacture proper .of the pawls is connected with difliculties, as a careful and exact hardening is imperative out of regard to the keeping ability.

The present invention relates to the production of a sewing-machine without said drawbacks which according to the invention is achieved in the way that the pawl-device for the locking of the presser foot and for the increase of pressure is replaced by a hydraulic pistondevice serving the same purpose. a

The invention is illustrated on thedrawing.

Figure 1 shows the presser foot with the hydraulic lockingand compression-device by sewing in relatively thin leather, and

Figure 2, the same parts by sewing in a thicker layer of leather.

In Figures 1 and 2, l is the-sewing table, 2 the presser foot, 23 the material to be sewn, 3the awl, and 26 the needle.

Presser foot 2 is, as is previously known, fastened to presser-foot-lever 4 that is rotatable around the fixed shaft 5 and actuated by spring 2| which latter keeps the presser foot down against the material (the shoe sole) resting on the sewing-table.

A piston 6 is, rotatable around a bolt I5, connected to the presser-foot-lever 4 said piston 6 may slide liquid-tight in a bore or cylinder 3!] 4 Claims. (01. 112-61) in a cylinder-block 1 provided with another bore 3| forming a cylinder for a second piston 12 the travel of which in said cylinder is controlled by 'a curve-slot 9 in a cam 29 fastened on driveshaft I9 by means of a suitable intermediate member, for instance, as shown a single-armed lever H rotatably connected to the piston and supported by roller Ill in the slot mentioned.

- wards in cylinder 3| it will primarily out off the channel I3 and thereby lock the presser foot 2 in such manner that the latter can not be lifted any longer at the subsequent perforation by the aw] 3, whereupon piston 12 during its further I travel in the cylinder 3i will force piston 6 outwards in cylinder 3! whereby the pressure of the presser foot against the material (the sole) will be increased, and consequently the various layers of leather will be well compressed, while the ma chine completes its stitch;

When piston I2 is once more withdrawn the presser foot will primarily be unloaded of the said extra pressure, and when piston i2 is carried that far rearwards that channel 13 will be re-opened, the locking of the presser foot will again be released (presser foot be unlocked), so that the latter may be lifted once more from the material against the pressure from the rather weak spring 2|.

As the motion for the presser foot for compressing the materialmust be larger, the thicker the material, proportion a on the drawing, the whole device is so designed that the alteration of the position of the presser-foot-lever, upon changing to material of larger thickness, see Figure 2 in comparison to Figure 1, will cause an angle-turning (V in Figure 2) of cylinderblock I which to this purpose is supported rotatably around a shaft [6. In this manner cylinder 3| will be carried a little higher up around piston l2 which therefore on its downward stroke will travel farther into the cylinder with the result that also the presser foot will perform a larger motion. In Figures 1 and 2, piston i 2 is in both cases shown in its innermost position. Proportions b indicate the effective travel of the piston in the two cases.

In order to regulate and adjust the pressure mentioned as desirable, the shaft I6 is supported ex-axially in the manner that, by turning the shaft, the entire cylinder-block may be raised or lowered, whereby the proportion b is increased or reduced.

Having thus described my invention what I claim is:

1. In a footwear sewing machine especially for welting, said machine including a rotatable main drive shaft, a sewing table, a presser foot adapted to be pressed against material to be sewn which is positioned on said table, and a presser foot lever mounted on said machine for pivotal movement with respect thereto, one end of said presser foot lever being secured to said presser foot, improved hydraulically-actuated means for operating said presser foot in a sequence of operations, first to lock said presser foot in contact with said material to be sewn whereby further movement of said presser foot away from said material is prevented, then to force said presser foot against said material with increased pressure, and finally to unlock said presser foot, thereby permitting movement of said presser foot away from said material, said hydraulically-actuated means comprising, in combination, two liquid-filled cylindrical chambers, said chambers being in communication with each other at their lower ends in a common liquid-filled bottom chamber; pistons sliding in said liquid-filled cylindrical chambers; means for moving one of said pistons in its liquid-filled chamber, said means being controlled from said drive shaft of said sewing machine and serving to move said piston in its liquid-filled chamber in response to rotation thereof; and means pivotally connecting one end of the other of said two pistons to said presser foot lever so that said presser foot lever is oscillated about its pivotal mounting in response to movement of said piston in its liquidfilled chamber, thereby forcing said presser foot against said material to be sewn and locking and unlocking said presser foot in the sequence of operations described.

2. In a footwear sewing machine as defined in claim 1, the construction in which said hydraulically-actuated means for operating said presser foot in said sequence of operations includes an auxiliary chamber for the reception of liquid, said auxiliary chamber being in communication "with said liquid-filled cylindrical chamber in which said piston whose movement is controlled from said drive shaft slides, said auxiliary chamber being open to the atmosphere and in communication with said liquid-filled cylindrical chamber through a port positioned in the side wall of said cylindrical chamber at a point which is below the lowermost position of said piston sliding in said cylindrical chamber when said piston is at its position of maximum outward travel therein, but above the lowermost position of said piston when said piston has travelled in said cylindrical chamber to its position of maximum inward travel therein, said piston thereby serving to shut off communication between said chambers through said port as it moves inwardly into said liquid filled cylindrical chamber, and to permit communication as it moves outwardly to its position of maximum outward travel in said cylindrical chamber, whereby said presser foot, which is actuated in its sequence of operations in response to movement of said piston in its cylindrical chamber, is not forced into locked position against said material being sewn until said piston on its inward travel into said cylindrical chamber has cut ofi communication between said chambers through said port, and is not unlocked until said piston on its outward travel in said cylindrical chamber has unblocked said port, thereby permitting liquid movement therethrough.

3. In a footwear sewing machine as defined in claim 1, the construction in which said cylindrical chambers form part of a pivotally mounted cylinder block, said cylinder block being pivotally mounted with respect to said sewing machine about an axis substantially parallel to the pivotal mounting of said presser foot lever, thereby permitting adjustment in position of said presser foot, said presser foot lever, and said piston pivotally connected thereto, whereby said presser foot accommodates itself to different thicknesses of material to be sewn on said sewing table.

4. In a footwear sewing machine as defined in claim 1, the construction in which said hydraulically-actuated means for operating said presser foot in said sequence of operations includes an auxiliary chamber for the reception of liquid, said auxiliary chamber being in communication with said liquid-filled cylindrical chamber in which said piston whose movement is controlled from said drive shaft slides, said auxiliary chamber being open to the atmosphere and in communication with said liquid-filled cylindrical chamber through a port positioned in the side wall of said cylindrical chamber at a point which is below the lowermost position of said piston sliding in said cylindrical chamber when said piston is at its position of maximum outward travel therein, but above the lowermost position of said piston when said piston has travelled in said cylindrical chamber to its position of maximum inward travel therein, said piston thereby serving to shut off communication between said chambers through said port as it moves inwardly into said liquid-filled cylindrical chamber, and to permit communication as it moves outwardly to its position of maximum outward travel in said cylindrical chamber, whereby said presser foot, which is actuated in its sequence of operations in response to movement of said piston in its cylindrical chamber, is not forced into locked position against said material being sewn until said piston on its inward travel into said cylindrical chamber has cut off communication between said chambers through said port, and is not unlocked until said piston on its outward travel in said cylindrical chamber has unblocked said port, thereby permitting liquid movement therethrough, said cylindrical chambers forming part of a pivotally mounted cylinder block, said cylinder block being pivotally mounted with respect to said sewing machine about an axis substantially parallel to the pivotal mounting of said presser foot lever, thereby permitting adjustment in position of said presser foot, said presser foot lever, and said piston pivotally connected thereto, whereby said presser foot accommodates itself to different thicknesses of material to be sewn on said sewing table.

VILHELM PEDERSEN.

No references cited. 

